GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B312A 02: Door Latch Actuators Enable Relay Control Circuit

DTC B312A 05: Door Latch Actuators Enable Relay Control Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Rear Access Panel Relay B+

2

2

--

--

Right Access Panel Release Signal

1, 2

1

1

--

Left Access Panel Release Signal

1, 2

1

1

--

Underhood Interlock Relay Control

B312A 02

B312A 05

B312A 05

--

LH Access Panel Relay Control

B250D 00

B250D 00

B250D 00

--

RH Access Panel Relay Control

B250E 00

B250E 00

B250E 00

--

Access Panel Latch Interlock Control

2

2

--

--

RH Access Panel Latch Control

2

2

2

--

LH Access Panel Latch Control

2

2

2

--

Rear Access Panel Switch Ground

--

1

1

--

Underhood Interlock Relay Ground

--

B312A 05

2

--

1. Rear Access Panel Switch Inoperative.

2. Rear Access Panel Latch Inoperative.

Circuit/System Description

The instrument panel cluster (IPC) monitors the circuit and if it detects a request for the rear access panels to activate, it will send B+ voltage to the interlock relay provided the vehicle speed is less than 3 km/h (1 mph). This will energize the relay and provide ground for the access panel actuators.

Conditions for Running the DTC

The system voltage is 9-16 volts.

Conditions for Setting the DTC

B312A 02

The IPC detects a short to ground in the LOCK relay coil control circuit.

B312A 05

The IPC detects a short to battery or an open/high resistance in the LOCK relay coil control circuit or an open/high resistance in the LOCK relay coil ground circuit.

Action Taken When the DTC Sets

Rear access panels will malfunction.

Conditions for Clearing the DTC

    • The DTC will be current for as long as the fault is present.
    • When the fault is no longer present, the DTC will be a history DTC.
    • A history DTC will clear after 50 ignition cycles.

Reference Information

Schematic Reference

Release Systems Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Access Panel Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Rear Access Panel Lock Relay Cmd. parameter while pressing and releasing the rear access panel switch, the parameter should change between Inactive and Active.

Circuit/System Testing

  1. Ignition OFF, disconnect the Door Lock relay.
  2. Test for less than 5 ohms between the relay coil ground circuit terminal and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Connect a test lamp between the relay coil control circuit terminal and ground.
  5. Ignition ON, command the Rear Access Panel Lock Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  6. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the IPC.
    If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the IPC.
  7. If all circuits test normal, test or replace the Door Lock relay.

Component Testing

  1. Ignition OFF, disconnect the Door Lock relay.
  2. Test for 60-180 ohms between terminals 85 and 86.
  3. If not within the specified range, replace the Door Lock relay.
  4. Test for infinite resistance between the following terminals:
  5. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    If not the specified value, replace the Door Lock relay.
  6. Install a 25-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
  7. If greater than the specified range, replace the Door Lock relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for IPC replacement, setup and programming